memory in mini mac problem

I have a new dual core minimac and it is supposed to have 80gb memory. I am running programs that are constantly stopping mid process complaining they do not have sufficient memory.

I am new to macs so not sure what is wrong, I have added up the memory usage in all the apps, itunes and folders etc and free space and it comes to only 40gb or so. Trash is empty, downloads cleaned out...etc etc. Is there some other setting on to activate more memory??? where is my other 40 gb?

yah sorry, it is disc space, not memory. apologies. 80gb and 512mb ram

I have three apps open only. 1 Final cut express, doing work with small 15 second ad clips. Clips are only 1gb and only ever work with one at a time. I clean out all the auto render,vault etc from FCE folder constantly and dump trash. Also running itunes and safari. That is it. I don't use Live type or any other programs at all, not even email.

It still sounds as though the message is 'insufficient memory' (ram), in which case you might find that it has to do with the type of video you are editing, or the number of effects you are trying to render.

What is the version of FCE? Are you capturing from tape or importing video files?